Silicon nitrides are well-known for outstanding properties such as its mechanical hardness, chemical inertness, and high electrical resistivity.1 These properties are used in a wide variety of applications. In contrast, the surface properties of silicon nitrides are still poorly defined and usually also changing over time. This situation significantly hampers the large-scale use of silicon nitrides in a variety of applications. The way out is to provide a well-controlled and stable surface modification to silicon nitrides. However, this has been problematic up to now.2 
However, surface modification of silicon oxides, and oxide-free silicon surfaces is well known in the art. Such functionalized oxide-free silicon surfaces having covalent organic mono-layers have been obtained by a variety of methods including thermal,3,4 mild photochemical5 or chemomechanical means.6 For example, reaction of 1-alkenes or 1-alkynes with H-terminated Si surfaces allows for the construction of tailor-made surfaces, and have provided e.g. the covalent attachment of DNA fragments7 and fragile carbohydrates.8 The present invention, however, is not directed to functionalization of silicon or silicon oxide surfaces, but to silicon nitride, silicon carbide, germanium nitride, germanium carbide and silicon germanium surfaces.
U.S. Pat. No. 6,569,979, incorporated by reference herein, points in detail to the relevance of surfaces that are suitable for immobilization of biologically active materials such as RNA, DNA and fragments or derivatives thereof U.S. Pat. No. 6,569,979 further discloses a method for modifying a non-oxidized silicon (001) surface, wherein functionalized 1-alkenes are reacted with hydrogen-terminated silicon under UV initiation. However, the method provides modified surfaces having a poor hydrophobicity as appears from the relatively low water contact angles. Modification by using tert. butoxycarbonyl protected 10-amino-1-decene afforded a modified non-oxidized silicon (001) surface having a water contact angle θ of only 78.1° C., i.e. near-identical to the value of non-modified hydrogen-terminated Si(001).
In contrast, modification of the silicon nitride surface has up to now largely been limited to the functionalization of the native SiO2 that is present as a poorly defined, thin layer on silicon nitride surfaces. For example, this procedure is used in the modification of silicon nitride AFM tips to obtain specific substrate interactions.9,10 Other examples of modified silicon nitrides include a poorly defined monolayer of 1-octadecene (static water contact angle θ=83°),11 and a carboxylic acid-functionalized monolayer via the N-alkylation of an ω-bromoalkanoic acid.12 
Cattaruzza et al., J. Mater. Chem. 14, 1461-1468, 2004, disclose that silicon nitride surfaces can be etched with HF to provide terminal —NH2 and —NH groups which can be converted in a subsequent step with ω-functionalized alkyl bromides. In the end product, the ω-functionalized alkyl groups are bonded to the silicon nitride surfaces via the reduced nitrogen atoms of the silicon nitride. The alkyl groups contain carboxyl, ester or amide functionalities (cf. entries 1, 2 and 13 of Table 1).
In this patent application, the silicon and/or germanium surfaces are generally defined as silicon nitride, silicon carbide, germanium nitride, germanium carbide and silicon germanium surfaces. Although these expressions are apparent to the person skilled in the art, a more specific definition of the silicon and/or germanium surfaces are surfaces comprising silicon and germanium nitrides according to the general formula M3Nx, wherein M is either Si or Ge and x is in the range of about 1 to about 4, silicon and germanium carbides according to the general formula MxCy, wherein M is either Si or Ge, x is in the range of about 0.3y to about 3y, as well as “strained silicon” which is known in the art as Si1-xGex wherein x is in the range of about 0 to about 1, preferably about 0.05 to about 0.95. It is well known in the art that the stoichiometry of these surfaces can continuously be varied, depending on the properties desired.
For brevity, in this application the abbreviation “Si/Ge-surfaces” is used to indicate silicon and/or germanium surfaces as defined herein.
“Strained silicon” contains germanium atoms in the crystal lattice with the result that the atoms are spread further apart than in neat silicon. In strained silicon, electrons experience less resistance and flow up to 70 percent faster compared to neat silicon which can lead to much faster chips. Strained silicon and methods of preparing strained silicon is for example disclosed in U.S. Pat. No. 6,464,780 and US 2004/0087119, both incorporated by reference herein.